Sankranti

A sankranti is the instant the Sun crosses from one sidereal sign into the next, and there are twelve of them in a year. This page prints all twelve for a chosen year with the local date and clock time of the ingress, the sign entered, and the date and time on which that solar month closes when the Sun leaves the sign again.

The instant is found by search rather than read from a table. The Sun advances about 0.985 degrees a day, so consecutive ingresses are up to about 30.5 days apart; the crossing is bracketed in a 32-day window and narrowed by bisection until the longitude sits on the 30-degree boundary.

The four cardinal ingresses carry their popular names, which this page labels Makara Sankranti with Uttarayana, Mesha Sankranti as the solar new year, Karka Sankranti with Dakshinayana, and Tula Sankranti.

The moment of the crossing is one thing; the calendar day on which the solar month begins is another, and the regional solar calendars genuinely disagree about it by up to two days. So four rules are computed in parallel and every result is labelled with the rule that produced it, following the Report of the Calendar Reform Committee (1955) p.244, "Rules of Samkranti".

The four are the Orissa Rule, the Tamil Rule, the Malabar Rule and the Bengal Rule, each in use in the region it is named for and each quoted on the row it produces. No agreement score is computed across them, because no source weights Bengal against Tamil against Malabar; where they differ, the difference is reported rather than averaged away.

With a chart active, the page reads the current solar month from the native's natal Moon. The Sun's gochara from the Moon is the sankranti phala: the house the Sun has entered, counted from the natal Moon's sign, is what the twelve-fold reading is keyed to. Phaladeepika 26.2 makes the Sun favourable in the 3rd, 6th, 10th and 11th from the Moon and nowhere else, and that is the table used, unchanged from the general gochara reading.

Two recensions of the twelve-fold reading are shipped and both are shown side by side: Phaladeepika 26.9 to 11 in V. Subrahmanya Sastri's translation, and Prashna Marga Ch. XXII stanzas 2 to 4 in B.V. Raman's, which that chapter's own first stanza credits to Varahamihira. They are independent transmissions of the same reading, they differ in wording and emphasis, and they are never merged into a third sentence that neither text contains.

Phaladeepika 26.25 places the Sun's fruit in the first decanate of the sign it has entered, that is the opening ten degrees, and the page dates that window from the ephemeris. Those ten degrees are not a third of the month: the Sun's daily motion varies through the year, so the window runs about ten days in January and about eleven in July, and the dates are read off the calculation rather than divided out of the calendar.

The obstruction layer is the same vedha machinery the general gochara reading uses, with the same pairs and the same immunity rules, so a month is not quietly given a different standard because the Sun is the graha in question. Where the Sun's vedha pairs cannot reach the house in play, the page says outright that no obstruction is possible that month rather than leaving an empty panel to be misread.

The twelve ingress instants are astronomy and do not depend on who is asking. Only the local clock time changes, with the timezone. The reading is counted from the natal Moon, so two people whose Moons are in different signs read the same ingress from different houses, and the same date carries two different readings.

This is also why the reading is keyed to the ingress instant rather than to a civil month-start day. The instant is identical everywhere; the civil day is precisely the thing the four regional rules disagree about, so hanging an interpretation on it would make the reading depend on which regional calendar the reader happened to be using.